Begin work on new box format

This commit just add the default /usr/share/lxc/templates/lxc-ubuntu
that comes with Ubuntu 12.10, added without changes in order to keep
track of what had to be done to suit vagrant-lxc needs
Change quantal-64 lxc template default user from ubuntu to vagrant
Remove bindhome support from quantal 64 lxc template
Build quantal 64 box with new json metadata
Tweak templates for quantal 64 to ease integration with vagrant
Remove cloud image related files
Handle new box metadata
Remove after create script support from box metadata
Extract rootfs tar contents into a tmp folder to avoid headaches and
check if a lxc-template file was included on .box
Update readme to use quantal64 box
Update example vagrantfile to use the quantl64 box
Use ubuntu mirrors for debootstrapping
Install curl, wget and bash-completion packages when building quantal64 base box
Rename rake task for building the base quantal64 box and prevent it from
running when box has already been built.
Improve readme and change Vagrantfile examples to use pre-built box from dropbox
Merge pull request #34 from fgrehm/new-box-format

New box format, drop support for ubuntu cloud image and start making use of a minimal quantal 64 box built with debootstrap